It is desirable that a chemical material is industrially excellent in storage stability, and does not show a change in form or property even when stored for a long time. In general, a polysiloxane having a reactive functional group such as a (meth)acryloyl group may be partially crosslinked, and may show a decrease in solubility in an organic solvent (or may become insoluble in an organic solvent) during storage singly. When the polysiloxane is stored as a polymer solution, a gel of the polysiloxane may be generated, or an insolubilized component may be precipitated in the solution. In particular, gelation or insolubilization occurs during the polysiloxane production process, and the target product may not be obtained.
Patent Literature 1 discloses a production method of a polysiloxane macromonomer that includes subjecting a reactive functional group containing alkoxysilane (A) such as γ-methacryloxypropyltrimethoxysilane and an alkoxysilane (B) such as tetramethoxysilane to hydrolysis and cocondensation in the presence of a solid catalyst (e.g., cation-exchange resin) that is insoluble in the system using water in a ratio from 70% to 140% by mol with respect to the total number of moles of the alkoxysilane (A) and the alkoxysilane (B). Patent Literature 1 describes that when an alkoxysilane is subjected to hydrolysis and condensation using a catalyst that is dissolved in the system (e.g., hydrochloric acid), hydrolysis and condensation progress with time, the reaction liquid shows an increase in viscosity, gelation is finally occurred, and storage stability is deteriorated.
Patent Literature 1 suggests that the hydrolysis rate differs depending on the type of alkoxysilane, but merely discloses subjecting only two alkoxysilanes (i.e., alkoxysilane (A) and alkoxysilane (B)) to hydrolysis at the same time. In some Example of Patent Literature 1, one of the two alkoxysilanes remains unreacted in an amount of 13% by mass. Specifically, a random cocondensation product may not be obtained, and a component having a high reaction rate may preferentially undergo hydrolysis and condensation when merely subjecting a plurality of alkoxysilanes that differ in reaction rate to hydrolysis and cocondensation in a mixed state. In particular, when the component having a high reaction rate is a tetrafunctional alkoxysilane (e.g., tetramethoxysilane) having a high valency, the condensation product tends to be strongly and three-dimensionally crosslinked. Therefore, a site in which the tetrafunctional alkoxysilane has preferentially reacted is three-dimensionally crosslinked to a large extent, and an increase in viscosity of the reaction mixture, and gelation or insolubilization easily occurs.
Patent Literature 2 discloses a production method of a condensation product that attempts to balance the reaction rates of two alkoxysilanes, and includes adding an organosilicon compound (A1) represented by R0(R1)nSiY3-n (wherein Y is a hydrolyzable group such as an alkoxy group) to a composition obtained by subjecting a tetrafunctional organosilicon compound (B1) represented by SiX4 (wherein X is a siloxane bond-forming group such as an alkoxy group) to an alcohol exchange reaction in 1-propanol, and subjecting the mixture to hydrolysis and copolycondensation under alkaline conditions. Patent Literature 2 states that this production method leads to a smooth progress of hydrolysis and copolycondensation to form an organosilicon compound (C1) as a more stable condensation product, and to a curable composition which is more excellent hardness and stability.
A polysiloxane produced by the process disclosed in Patent Literature 2 shows some difference in stability depending on the conditions.
A reactive polysiloxane has been increasingly used in various applications along with the development of industry, and a process that can more easily produce a more stable polysiloxane has been desired.